Electrical stimulation electrode

ABSTRACT

A transcutaneous nerve and/or muscle stimulation electrode is provided which may be contoured to the skin areas of a patient and stretched therewith while impulse signals are electrically conducted into the body. This stretching ability is provided by a conductive fabric which includes an array of conductive fibers with interstitial areas therebetween. A conductive adhesive fills interstitial areas of the conductive fabric and provides for adhering the electrode to the patient&#39;s skin.

This application is a continuation-in-part of U.S. patent applicationSer. No. 745,018, filed June 14, 1985, now U.S. Pat. No. 4,722,354,issued Feb. 2, 1988.

The present invention generally relates to electrodes and, moreparticularly to electrodes suitable for transcutaneous nerve and/ormuscle stimulation.

Continued development of electrical medical devices has produced a needfor a variety of electrodes.

Although many of these electrodes have, as a design objective, goodelectrical signal transmission between a patient's skin surface andelectrical leads interconnected with a device, each has specificrequirements dependent upon the type of apparatus for which it is to beused.

As an example, electrocardiograph (EKG) and electroencephalograph (EEG)machines are primarily monitoring type devices which require smallcontact surfaces, or area, with the patient's skin.

On the other hand, transcutaneous electric nerve stimulation (TENS), andmuscle stimulation devices require relatively large skin surface contactto effect such nerve and muscle stimulation.

Transcutaneous electrical nerve stimulation is useful, for example, inpost-operative and chronic pane control, while muscle stimulation isuseful, for example, in maintaining and development of muscle tissue.Electrodes suitable for use in nerve and muscle stimulation preferablyprovide a uniform electrical coupling across the skin electrodeinterface.

As hereinbefore noted, electrodes suitable for nerve and/or musclestimulation may be relatively large having dimensions of several inchesor more.

Because nerve and/or muscle stimulation causes muscle contraction, aconsiderable amount of skin movement is associated therewith.

Additionally, perspiration from the skin is more likely to loosen ordisrupt the electrode because of its large size. As should be apparent,the larger the electrode, the longer the evaporation path, or distance,the perspiration occurring at the center regions of the electrode musttravel in order to evaporate, or be released to the atmosphere.

It has been found that prior art electrodes which have been secured tothe surface of a patient's skin with medical adhesive tape, or the like,have a tendency to lift off from the skin because of perspiration andmovement of the patient's skin during treatment.

Because an electrode suitable for nerve and/or muscle stimulation mustprovide for an electrical signal to be distributed over the entiresurface of the elecrtrode, the electrode must necessarily be conductive.

Prior art electrodes have utilized a number of conductive elements, suchas carbon impregnated rubber and vinyl, as well as metallic foils.

However, a useful electrode must be flexible in order to accommodaterelative movement of the patient's skin therebeneath, ashereinabove-described.

Because nerve and muscle stimulation electrodes may be utilized overalong period of time, as may be necessary in connection with sportsinjuries, the electrode must be compatible with the skin and flextherewith.

Insufficient flexing of the electrode can result in severe irritation ofthe patient's skin and electrical "hot spots" due to unevenelectrode-skin contact, which manifests itself in a rash and a burningsensation.

The sensation of burning may be sensed by the patient within a fewminutes after application of electrical signals during nerve and/ormuscle stimulation, while the rash conditions generally take a longerperiod of time to develop.

It has been found that the use of prior art electrodes in nerve and/ormuscle stimulation results in a skin rash in up to 25% to 35% of thepeople undergoing treatment.

An additional problem associated with the necessary stretchability ofelectrodes utilized in nerve and/or muscle stimulation procedures isthat while the electrode must be able to flex, or stretch, in order toaccommodate skin movement during treatment, the conductivity of theelectrode should not be interrupted, or distorted, due to the stretchingof the electrode.

Prior art electrodes have comprised the flexibilty of the electrode inan effort to provide uniform current densities over the entire contactarea of the electrode. These electrodes typically utilize a metallicmesh, or foil, to provide contactivity of the electrode and utilize aconductive gel between the electrode and the patient's skin in order toaccommodate movement therebetween.

There is, however, relative movement between the relatively rigidelectrode and the skin, which is accommodated for by the gel. Thisrelative movement oftentimes causes the gel to move from beneath theconductive portion of the electrode, thereby limiting the useful life ofthe electrode on the skin.

In addition, this relative motion between the skin and the electrodedoes not provide for the maintenance of the position of the electroderelative to the nerve and/or muscle being stimulated.

Precision positioning of the electrode is, of course, performed by aphysician, or the like, knowledgeable in the treatment method.Inaccurate placement of the electrode, or slipping of the electrode fromits intended position, may significantly reduce the beneficial effectsof the treatment.

Hence, there is a need for a flexible electrode for use with electricalstimulation devices which adheres well to the patient's skin, is easilyremoved therefrom, and is able to move with the patient's skin in orderto ensure proper continuous placement of the electrode relative to nerveor muscle tissue being stimulated, as well as providing long-termcontinuous electrical connection therewith without irritation of theskin or discomfort to the patient under treatment. The electrode of thepresent invention fulfills these needs.

SUMMARY OF THE INVENTION

A flexible transcutaneous electrical nerve and/or muscle stimulationelectrode in accordance with the present invention includes a conductivefabric comprising an array of conductive fibers with interstitial areastherebetween.

Flexible conductive adhesive means are provided and disposed within theinterstitial areas and on one side of the conductive fabric for adheringthe flexible transcutaneous electrical nerve and/or muscle stimulationelectrode to the skin of the patient and providing an electricalconducting contact therebetween.

Interconnection with an electrical stimulation device is provided bymeans of an electrical lead wire, which is interconnected with theconductive fiber and adapted for interconnection with the electricalstimulation device.

A non-conductive sheet is disposed on the other side of the conductivefabric for preventing undesired electrical contact therewith.

More particularly, the conductive fabric may comprise woven conductivefibers which enables the conductive fabric to be stretched up to 20percent greater than the original conductive fabric dimensions in thedirection of stretch. Alternatively, the conductive fabric may comprisea honeycomb latch needle knit which is capable of being stretched up toabout 100 percent greater than a first original conductive fabricdimension and capable of being stretched up to about 20 percent greaterthan a second original conductive fabric dimension.

Utilization of this knit enables significant stretching of the electrodewithout a decrease in the conductivity of the fabric. The resultingflexible transcutaneous electrical nerve and/or muscle stimulationelectrode has more stretch in one direction than in an oppositeorthogonal direction; however, during use, the primary motion of theskin beneath the electrode as a result of a nerve and/or musclestimulation is, in one direction, along which the primary stretchdirection of the electrode is aliged.

Conductivity of the conductive fabric is provided by the conductivefiber which may include a blend of stainless steel and polyester, withthe stainless comprising about 20 percent by weight of the result infiber and the polyester comprising about 80 percent by weight of theconductive fiber.

The non-conductive sheet may be any suitable stretchable plastic, whichis held against the conductive fabric by means of a pressure sensitiveadhesive.

The non-conductive sheet and the pressure sensitive adhesive are alsooperative for holding the electrical wire lead against the conductivefabric to provide electrical contact therebtween. This contact isenhanced by utilizing a stranded electrical lead wire, which may bestainless steel, and fraying an end portion thereof to thereby providegreater contact area between the electrical lead and the conductivefabric.

DESCRIPTION OF THE DRAWINGS

The advantages and features of the present invention will be betterunderstood by the following description and drawings in which:

FIG. 1 is a perspective view of a flexible transcutaneous electricalnerve and/or muscle stimulation electrode in accordance with the presentinvention showing its disposition on a patient's skin;

FIG. 2 is a perspective view of the stimulation electrode with a portionof a non-conductive sheet thereof peeled back to show an electrical leadwire therein;

FIG. 3 is a cross-sectional view of the transcutaneous electrical nerveand/or muscle stimulation electrode generally showing conductive fabric,a flexible conductive adhesive, electrical lead wire, non-conductivesheet and a pressure sensitive adhesive;

FIG. 4 is an enlarged view of the conductive fabric utilized in thepresent invention generally showing a honeycomb latch needle knit;

FIG. 5 is an illustration of the conductive fabric utilized in thepresent invention stretched in a transverse direction;

FIG. 6 is an illustration of the conductive fabric utilized in thepresent invention stretched in a longitudinal direction; and

FIG. 7 is an illustration of woven conductive fabric suitable for use inthe present invention.

DETAILED DESCRIPTION

Turning now to FIGS. 1 and 2, there is shown, in perspective view, aflexible transcutaneous electrical nerve and/or muscle stimulationelectrode 10 in accordance with the present invention.

As shown in FIG. 1 and hereinafter described in greater detail, theelectrode 10 is flexible in two directions, as indicated by arrows 14,16, while in place on a patient's limb 20, or body, not shown. As moreclearly shown in FIG. 3, the electrode 10 includes a stretchableconductive fabric 22, flexible conductive adhesive 24, which is disposedon one side 28 of the conductive fabric 22 for adhering the flexibletranscutaneous electrical nerve and/or muscle stimulation electrode 10to the skin of a patient (not shown in FIG. 3) and electrical lead wire30 interconnected with the conductive fabric 22 as hereinafterdescribed, for providing electrical signals to the conductive fabric 22when interconnected with an electrical stimulation device, not shown, bymeans of a connector 34, or the like.

In addition, a non-conductive sheet, such as a flexible plastic 32disposed on another side 36 of the conductive fabric 22 by means of apressure sensitive adhesive 38, provides means for preventing undesiredelectrical contact with the conductive fabric 22, as may occur duringwearing of the device.

It should be appreciated that the conductive fabric 22 must be insulatedfrom outside objects and other areas of the patient's skin in order topreferentially couple electrical signals into the patient's body whereprescribed by an attending physician.

It has been found that a knit fabric, preferably a one-quarter-inchhoneycomb latch needle knit fabric, as depicted in FIG. 4, provides fora fabric which may be stretched up to about 100 percent greater than afirst original conductive fiber dimension in the direction of stretch,see arrow 40 and FIG. 5, and up to about 20 percent greater than asecond original fabric dimension in a second direction of stretch, seearrow 42 and FIG. 6, without loss of conductivity of the fabric. Knitsof this nature are commercially available from knitters, such as, forexample, Paragon West Knitting Mill in Anaheim Hills, Calif.

Woven fabrics, such as illustrated in FIG. 7, are also suitable if lessstretch is required, as may be the case when the electrode is utilizedon less curvature portions of the body, such as the back.

The conductivity of the fabric is provided by the individual conductivefibers 46. It has been found that a conductive fiber No. BK50/2manufactured by Bakaert of Belgium, which includes a blend of 20 percent316 stainless steel and 80 percent of polyester when latch needlehoneycomb knitted to a density of about 2.5 pounds per square yard,produces a conductive double-stretch knit which is particularly suitablefor transcutaneous nerve and/or muscle stimulation electrodes.

The double-stretch nature of the knit fabric, when incorporated into theelectrode of the present invention, as hereindescribed, provides for anelectrode which is contourable to the shape of a patient's body or limb.

This is particularly important with relatively largestimulation/electrodes in accordance with the present invention. Theelectrode 10 may have dimensions in the range of, for example, 2 inchesby 3 inches, hence, the electrode must be "fitted" by stretching of theelectrode 10 to the skin 20 of a patient in order to provide a uniformcontact therebetween.

It is particularly important that the electrode 10 and, of course, theconductive fabric 22, do not degrade during constant and repetitiousmovement and stretching thereof, as the electrical signals activatemuscles and nerves within the patient's body which result in continuedmovement, or contraction, of the skin. Because the conductive fabric isa loose knit, stretching thereof does not deteriorate any of theconductive fibers therein to any substantial degree, thus causing lossof conductivity of the electrode.

In order to be effective in transmitting electrical signals to thepatient's skin 20, the electrode 10 utilizes a conductive adhesive 24,such as one manufactured by Valley Lab, Inc., of Boulder, Colo., underthe name Polyhesive, this proprietary product is useful in a number ofelectrode applications and has the advantage of being flexible so thatit will move with the conductive fabric without losing contact with thepatient's skin, or interrupting the electrical signals transmittedtherethrough.

In the manufacture of the electrode 10, the conductive adhesive 24 ispoured onto the surface 28 in a liquid form, whereupon it fills theinterstitial areas 50 of the conductive fabric 22.

Thereafter, the adhesive is set into a gel-like material, which has goodadhesion to the patient's skin, and is releasable therefrom without theannoyance of hair-pulling and the like. The conductive adhesive 24 iscommercially available and is compatible with the skin in that itproduces no irritation thereof.

Because the Polyhesive conductive adhesive 24 is in itself flexible, itdoes stretch with the conductive fabric between the interstitial areas50 defined by the fibers 46.

Turning to FIGS. 2 and 3, the non-conductive plastic, or backing layer,32 is adhered to the other side 36 of the conductive fabric 22, and boththe backing layer and the pressure sensitive adhesive 38 hold the leadwire 30 in physical and electrical contact with the conductive fabric.In order to enhance contact therebetewen, the conductive lead 30, whichmay be stranded stainless steel, has an end portion 54 which is frayedand spread apart slightly.

In manufacture, the conductive lead is placed on the conductive fabric22 for a distance of about one-third the length thereof. Thereafter, thebacking layer 32, with adhesive 36 applied thereto, may be firmly placedover the frayed portion 54 and bonded by pressure applied thereto.

This relatively simple method of contacting the lead wire 30 with theconductive fabric 22 enables some movement therebetween as theconductive fiber and electrode stretch.

It should be appreciated that stretching along the direction 40, themajor direction of stretch, may stretch the frayed strands 58 apart fromone another, thus reducing the relative motion between the frayed end of54 and the conductive fiber 22.

Because the conductive adhesive 24 is subject to drying, a release liner60 may be provided for storage of the electrode before and after use.This liner may be of any suitable plastic, or silicon-coated paper,which is strippable from the conductive adhesive 24 without disturbingthe integrity of the conductive adhesive.

Although there has been hereinabove-described a specific arrangement ofa flexible transcutaneous electrical nerve and/or muscle stimulationelectrode in accordance with the invention for the purpose ofillustrating the manner in which the invention may be used to advantage,it will be appreciated that the invention is not limited thereto.Accordingly, any and all modifications, variations, or equivalentarrangements which may occur to those skilled in the art, should beconsidered to be within the scope of the invention as defined in theappended claims.

What is claimed is:
 1. A flexible transcutaneous electrical nerve and/ormuscle stimulation electrode comprising:a conductive fabric comprisingconductive fiber means for both enabling the conductive fabric to bestretched, and for directly coupling electrical signals to a patient'sskin, said conductive fabric comprising an array of conductive fiberswith interstitial areas therebetween; flexible solid conductive adhesivemeans disposed within said interstitial areas and on one side of saidconductive fabric for both adhering the flexible transcutaneouselectrical nerve and/or muscle stimulation electrode to the skin of apatient and providing an electrical conducting contact therebetween;electrical lead wire means interconnected with said conductive fabricand adapted for interconnection with an electrical stimulation devicefor providing electrical signals to said conductive fabric; and,non-conductive sheet means disposed on another side of said conductivefabric for preventing undesired electrical contact with the conductivefabric.
 2. The flexible transcutaneous electrical nerve and/or musclestimulation electrode according to claim 1 wherein the conductive fibermeans comprises woven conductive fibers and said flexible solid adhesivemeans comprises a material of sufficient flexibility to stretch withinthe interstitial areas and along the one side of the conductive fabricto enable the conductive fabric to be stretched without the flexiblesolid adhesive means separating from the conductive fibers.
 3. Theflexible transcutaneous electrical nerve and/or muscle stimulationelectrode according to claim 2 wherein said conductive fiber comprises ablend of stainless steel and polyester.
 4. The flexible transcutaneouselectrical nerve and/or muscle stimulation electrode according to claim3 wherein the conductive fiber comprises about 20 percent by weightstainless steel and about 80 percent by weight polyester.
 5. Theflexible transcutaneous electrical nerve and/or muscle stimulationelectrode according to claim 2 further comprising pressure sensitiveadhesive means for holding said non-conductive sheet means to theconductive fabric and for contacting the electrical lead wire means withthe conductive fabric.
 6. The flexible transcutaneous electrical nerveand/or muscle stimulation electrode according to claim 5 wherein theelectrical lead wire comprises stranded stainless steel and thenon-conductive sheet means and pressure sensitive adhesive means supporta portion of the stranded stainless steel against and along the lengthof the conductive fabric for a distance of about one-third the length ofconductive fabric.
 7. The flexible transcutaneous electrical nerveand/or muscle stimulation electrode according to claim 6 wherein theelectrical lead wire portion in contact with the conductive fabric isfrayed into individual strands and disposed so that stretching of theconductive fabric causes the frayed individual strands to separate andmove with the conductive fabric.
 8. A flexible transcutaneous electricalnerve and/or muscle stimulation electrode comprising:a conductive fabricmeans comprising woven conductive fibers with interstitial areastherebetween for directly coupling electrical signals to a patient'sskin; flexible solid conductive adhesive means disposed within saidinterstitial areas and on one side of said conductive fabric for bothadhering the flexible transcutaneous electrical nerve and/or musclestimulation electrode to the skin of a patient and for directly couplingelectrical signals to the patient's skin; electrical lead wire meansinterconnected with said conductive fabric and adapted forinterconnection with an electrical stimulation device for providingelectrical signals to said conductive fabric means, said electrical leadwire means comprising stranded wire having a portion thereof frayed forincreased contact with said conductive fabric means; non-conductiveflexible plastic means disposed on another side of said conductivefabric means for preventing undesired electrical contact with theconductive fabric means; and pressure sensitive adhesive means forholding said non-conductive flexible plastic means and said electricallead wire means to the conductive fabric means.
 9. The flexibletranscutaneous electrical nerve and/or muscle stimulation electrodeaccording to claim 8 wherein said flexible solid adhesive meanscomprises a gel material of sufficient flexibility to stretch within theinterstitial areas, without the flexible solid adhesive means separatingfrom the conductive fibers.
 10. The flexible transcutaneous electricalnerve and/or muscle stimulation electrode according to claim 9 whereinsaid conductive fiber comprises a blend of stainless steel andpolyester.
 11. The flexible transcutaneous electrical nerve and/ormuscle stimulation electrode according to claim 10 wherein theconductive fiber comprises about 20 percent by weight stainless steeland about 80 percent by weight polyester.
 12. A flexible transcutaneouselectrical nerve and/or muscle stimulation electrode comprising:aconductive fabric comprising conductive fiber means for both enablingthe conductive fabric to be stretched up to at least about 20 percentgreater than the original conductive fabric dimension in the directionof stretch and for directly coupling electrical signals to a patient'sskin; said conductive fiber means comprising an array of wovenconductive fibers with interstitial areas therebetween; flexibleconductive adhesive means disposed within said interstitial areas and onone side of said conductive fabric for both adhering the flexibletranscutaneous electrical nerve and/or muscle stimulation electrode tothe skin of a patient and for directly coupling electrical signals tothe patient's skin; electrical lead wire means interconnected with saidconductive fabric and adapted for interconnection with an electricalstimulation device for providing electrical signals to said conductivefabric, said electrical lead wire means being frayed into individualstrands and disposed so that stretching of the conductive fabric causesthe frayed individual strands to separate and move with the conductivefabric; non-conductive sheet means disposed on another side of saidconductive fabric for preventing undesired electrical contact with theconductive fabric.